When I tried to deposit Al, heavy arcing occurred at the first time. I slowly controlled the power controller I managed it. But there was an oscillation of power between 98W to 103W. It was periodic and it seemed to arc again when I saw the status of plasma through the view port. I don't know what have happened . It could be temporary or not. Maybe that would be great if the next user check the status of it (arcing or not).